1. Field of the Invention
The present invention relates to an automatic cash dispenser installed in a banking system, and particularly to an apparatus for and a method of discriminating denominations and authenticity of banking bills (hereinafter referred to as bills).
2. Description of the Related Art
A typical cash dispenser has a bill discriminating apparatus for discriminating denominations of and authenticity of bills deposited by customers or for ascertaining denominations of and authenticity of bills to be drawn by the customers.
The bill discriminating apparatus of this type has a sensor disposed opposite to a bill which travels in the cash dispenser and is to be discriminated (hereinafter referred to as discriminated note) for ascertaining the genuineness of bills. The sensor includes a magnetic sensor for detecting a mangetic property of magnetized ink employed in the discriminated bill.
The sensor first detects one side of the bill, i.e. a face or a back, in the vertical direction relative to the traveling direction of the bill (main scanning direction) and thereafter in the lateral direction relative to the traveling direction as the bill travels further (auxiliary scanning direction), thereby reading an entire printed pattern of the bill to extract therefrom the printed pattern in a specific area which is determined by the traveling direction.
The thus read printed pattern in the specific area is converted by the sensor into an electrical signal which varies in amplitude. The electrical signal has a characteristic value depending on the difference between the denomination of bills and the traveling directions of the bills.
The sensor comprises an image sensor or the like and outputs a continuous analog signal which varies in amplitude as the discriminated bill travels. The analog signal is sampled for a predetermined time interval and converted into a digital signal by an A/D converter. Consequently, a plurality of digital scale data (data signal to be discriminated, hereinafter referred to as discriminated signal) are produced in every discriminated bill depending on the read electrical signals.
The bill disciminating apparatus has stared standard pattern signals to be compared with the discriminated data signal. The standard pattern signals have upper and lower limit values. The bill discriminating apparatus compares the discriminated data signals with the standard pattern signals to see that they are within the upper and lower limit values and carries out an arithmetic operation based on the result, which has been obtained at many sampling points, thereby discriminating the denomination of bills and the traveling direction.
The standard pattern signal is typically produced in the following manner.
First, the sensor reads a plurality of printed patterns of genuine bills and collects electrical signals corresponding to the read printed pattern.
Even in the same denominations of bills, the scanning area is differentiated in the case where the traveling bill confronts the sensor at the left side of the face thereof and in the case where the traveling bill confronts the sensor at the right side of the face thereof, whereby the standard pattern is differentiated. In the case of the back of the bill, it is same as in the case of the front of the bill. Accordingly, since there are three denominations of the Bank of Japan bill, i.e., 10,000-yen bill, 5,000-yen bill and 1,000-yen bill, four denominations of standard pattern signals are determined for each denomination of bill, considering the face of the bill, i.e. denomination, the back of the bill and the traveling direction.
However, the selection of an optimum scanning area in every bill required much time and labor since it was necessary to collect an extensive amount of printing data in every face, back and traveling direction.
If the printing data is obtained merely from a less soiled genuine bill, a genuine bill is liable to be often rejected as a false bill since the discriminating standard becomes strict.
Furthermore, inasmuch as the picture element of the image sensor employed in the sensor is very minute, the scanning line in the main scanning direction is subsegmented while the scanning line in the auxiliary scanning direction becomes a continuous line since ordinary bills have printed shear or crumple thereof, the detected data is liable to scatter widely since it is difficut to obtain the same auxiliary line at all times when the auxiliary scanning lines are minute.
If the authenticity or the denomination of bill is discriminated on the basis of the widely scattered data and the previously prepared standard pattern, the discrimination accuracy is deteriorates.
Furthermore, the discriminated data signal has to be collated with many standard pattern signals to improve the discriminating accuracy based on such data. As a result, such a discriminator collation takes much time for collation and requires a large storage capacity to store many standard pattern signals.